Isomerization process



June 17, 1947. o. GERBES 94 29 ISOMERIZATION PROCESS Filed Jan. 12, 1945 Make-Up 35 V I5 HCI 2| 1 r; Vent Gases I o- I2 I A Inert Gas F l8 f I as Make-Up Carolyn +Minimum Chloride 4-.

i 34 25 ll\ N-Poraffin Feed -Rccyclc N-Pcroffin 0H Ispmerizad Product v54 F a. 52 v Catalyst j 52 55 fikon INVENTOR.

ATTORNEY.

Patented June 17, 1947 ISOMERIZATION PROCESS Otto Gerbes, Goose. Creek, Tex., assignor to Standard Oil Development Company, a corporation of Delaware Application January 12, 1945, Serial No. 572,493

3 Claims.

The present invention relates to the production of a tenacious, protective coating of carbonaceous material and to the application of such coatings to metal surfaces exposed to corrosive conditions. The present invention is further directed to a process for the isomerization of parafiin hydrocarbons in the presence of a vaporized aluminum halide and wherein corrosion of equipment employed for producing the isomerization reaction is prevented by forming a protective coating on surfaces with the use of the same agent as is employed as a catalyst in the isomerization reaction.

when conducting chemical reactions, it often happens that corrosive materials are present in the reaction zone which are corrosive to metals commonly used in constructing such reaction vessels. The isomerization of paraffin hydrocarbons in the presence of aluminum chloridehydrocarbon complexes or sludges and aluminum chloride-inorganic salt melts may be considered to exemplify such reactions. These types of catalyst are efiective in catalyzing the isomerization reactions of the type mentioned before but have the disadvantage of being highly corrosive to ferrous metallic vessels in which the isomerization reaction takes place. It has been necessary to resort to vessels having alloy linings of metals resistant to the corrosive attack of the catalyst or cement linings gunited upon the interior of the reactor vessels. Both of these expedients are disadvantageous since the alloy linings are quite expensive and difiicult to install While the gunited linings are subject to spalling and mechanical deterioration in service. Both types of linings are time-consuming with regard to installation, require frequent inspection and refabrication and are thus expensive from all standpoints.

In accordance With the present invention, a tenacious, resistant, protective coating of carbonaceous material is deposited on metallic surfaces and the application of the coating may, if desired, be carried out in connection with an isomerization reaction to protect the surfaces of the equipment employed for the isomerization reaction against the corrosive catalyst used in the reaction. The protective coating of the present invention'is produced by spraying, flowing or otherwise depositing a film of a reactive hydrocarbon or mineral oil upon the selected surfaces, preferably upon surfaces exposed to corrosive attack. Either prior or subsequent to the deposition of the hydrocarbon film, the surface is brought to a temperature of at least 150 F.

by convenient means, such as by heating with a superheated gas, and aluminum halide in a vaporized form is passed in contact with the film of hydrocarbon at a temperature of at least R, but preferably in the range of 200 to 300 F.

The aluminum halide employed to treat the film may be carried by gas, such as nitrogen, air or it even may be carried by the vaporized feed hydrocarbon. Usually it will be desirable to employ a carrier gas other than the hydrocarbons for the aluminum halide since the hydrocarbons if employed, may dilute the film formed upon the surface to be treated. 'Ih'e aluminum halide is preferably vaporized by passage of an inert carrier gas through a body of aluminum halide at a temperature of about 150 F. but preferably in the higher range mentioned at a convenient pressure but at a sufficient temperature to obtain sublimation of the aluminum halide. The aluminum halide-containing vapors are directed into the equipment so that contact is made with all desired surfaces. In a matter of a few minutes after the attainment of reaction temperature, a hard film is deposited by reaction of the aluminum halide vapors with the film of mineral oil.

In the practice of the present invention, a heavy hydrocarbon may be employed, such as a mineral oil of a parafiinic nature. A light lubricating oil, such as an S. A. E. 10 lubricating oil, may be used but it is also contemplated that a lighter oil of the type of the so-called solvent oils may be injected into the equipment to form the protective film. Alternatively, a heavy lubrieating oil may be used.

As mentioned before, the aluminum halide may be carried by hydrocarbon vapors but since the hydrocarbon vapors may dilute the heavier hydrocarbon film, it may be preferred to employ a non-hydrocarbon gas which has little tendency to dilute the aforementioned film of a mineral oil.

The invention will be described further by reference to the drawing in which Fig. 1 is a flow diagram of one embodiment, showing the injection of oil and the treatment of the film formed by the injection of the oil with aluminum chloride vapors; and

Fig. 2 is another embodiment in which a lined reactor is treated to prevent leakage of the corrosive material to the ferrous metal surfaces.

Referring now to the drawing and to Fig. 1 in particular, numeral I i designates a feed line through which a normal paraffin, such as normal pentane, is introduced into the system. The feed line H connects to the bottom of a reactor l2 which may be a packed tower or an open vessel. Reactor I2 is provided with a line l3 for injection of oil thereto and means M for distributing said oil, line l5 for conducting reaction products from the reactor 12, line I6 for introduction of catalyst and line I! for withdrawal of catalyst.

For purposes of description, reactor l2 will be considered to be a reactor containing a suitable packing, such as quartz chips, bell cap plates or other distributing means. Prior to the initiation of the isomerization reaction, an inert gas introduced by Way of line I 8 controlled by valve I9 is passed into vessel 20 which contains an aluminum halide. The inert gas is heated to a suitable temperature in the range between 150 and 300 F. and is passed through the body of aluminum halide in vessel 20. The inert gas picks up aluminum halide vapors by sublimation on passage through the body of aluminum halideand discharges from vessel 20 by line 2| which connects into line H. Prior to the passage of aluminum halide-containing vapors into the reactor [2, the interior surface of the Wall thereof is brought up to a suitable temperature and oil is introduced into the reactor through line it by distributing means 14 under conditions to form a film throughout the interior surface of the reactor 12. The vapors of aluminum halide contacting the oil film on the interior surface of the reactor vessel forms an impervious resistant film. The. inert gas is then shut off from the system by closing valve l9 and oil passing through line [3 is also out out by closing valve 22. Valve 23 in line Ii is then opened allowing introduction of normal parafiin feed into line H. As the hydrocarbon is introduced into the reactor vessel l2, an amount of aluminum halide catalyst of the type mentioned hereinbefore sufiicient to catalyze the isomerization reaction is introduced through line 24v controlled by valve 25. When the system has been provided with suflicient aluminum chloride to catalyze thereaction, valve 25 may be closed off and only a sufficient amount of catalyst to maintain the activity of it at an optimum level may be introduced intermittently, the remainder being provided by recycling catalystwithdrawn from the bottom of the reactor by Way of line I1 and pump 26. From time to time-it may be necessary to discard an amount of catalyst equivalent to the amount of a makeup catalyst introduced by line 24. This may be accomplished by opening valve 21 in line H.

The isomerized hydrocarbons are discharged from the reactor l2 by way of line l5 and pass through a condenser or cooler 28 and thence into an accumulator 29 wherein light hydrocarbons which may be produced by the reaction are vented through line 30 and the isomerized product, promoter and unreacted hydrocarbons are discharged through line 3| into a stripping tower 32.

Stripping tower 32 is provided with a heating means 33 by which temperature and pressure conditions are adjusted to allow recovery of promoter gas which isnecessary to promote the catalytic effect of the aforementioned type of aluminum halide catalyst. The promoter is discharged from stripper 32 by way of line 34 and is introduced thereby back into line It. Any promoter which may be consumed in the reaction may be supplemented by the addition of make-up promoter, which is ordinarily a hydrogen halide, by opening valve 35 in line 36.

The isomerized hydrocarbons and unreacted hydrocarbons are discharged from stripper 32 by way of line 31 into a second stripper 38 which similar to stripper 32 is also provided with a heating means which in this instance is designated by the numeral 39. Conditions are adjusted in stripper 38 to recover by way of line it the desirable isoparaffin and to discharge by line 4i unreacted normal paraifin which is recycled thereby to line ll.

Prior to the present invention in which the interior surfaces of the reactor vessel l2 are provided with a film of carbonaceous matter resistant to the corrosive action of the aforementioned aluminum halide catalyst, it was necessary to terminate the reaction at frequent intervals for repair of the reaction vessel l2 and any of the auxiliary equipment which came in contact with the catalyst.

Turning now to Fig. 2, another application of the present invention is the treatment of lined reaction vessels, such as those lined with an alloy lining. One great objection to lined reactor vessels is the frequent cracking of these vessels by stresses and strains incident to their installation or the joining of a lining Of one composition to a vessel of another. When such leaks occur in lined vessels, the corrosive catalysts have in gress to the ferrous metal surfaces of the reaction vessel and consequently cause their ultimate destruction. When treating vessels in connection with the embodiment of the present invention, a reactor vessel 5% containing an alloy lining 5! is provided with ports 52 for introduction of oil between the surfaces of the vessel 5% and the lining 5|. I'he vessel 55 is also provided with a line 53 by Way of which paraffin hydrocarbons may be introduced, outlet line 5:1 for discharge of isomerized product, a second inlet line 55 for introduction of catalyst and a second outlet line 56 for withdrawal of catalyst from the vessel 50.

The reactor vessel 52) may be provided with suitable packing material indicated by the shaded portion 51. This packing material may comprise quartz chips, plates, or other distributing means well-known to the art.

For purposes of illustration only, it is assumed that the lining 5% has suffered deterioration by cracking and leaks of hydrocarbon have shown up by virtue of the maintenance of a higher pressure in the interior space of the vessel til than in the space between the lining 5! and the vessel 58, the hydrocarbons being detected by appearing in the ports 52. When it has been determined that the lining has suffered deterioration, a parafflnic oil reactive with aluminum halide is introduced into the space between the vessel 50 and the lining 5| through the ports 52, excess oil being discharged through port 49. The vessel is brought up to a temperature of between and 300 F. either prior to or after introduction of the oil and vaporized aluminum halide is then introduced through the ports 52 to cause reaction between the aluminum halide and the film formed on the exposed surfaces of both the vessel 5% and the lining. By practicing this expedient, both the vessel 50 and the lining 5! may be effectively protected against the corrosive activity of the aluminum halide catalyst of the types mentioned.

As another embodiment of the present invention in accordance with the embodiment of Fig. 2, the oil employed as the basis for the resistant film formed on the interior of the lining at the reactor surface may be introduced into the space defined by the lining rather than in the space defined by the vessel and the lining whereby any cracks in the lining would be eifectively sealed.

In conducting isomerization in equipment treated in accordance with the present invention, it is contemplated that a promoter for the reaction, such as hydrogen halide, may be employed. It is contemplated also that the aluminum halide. such as aluminum chloride or bromide, and other active aluminum halides may be employed as the catalyst as a complex with organic or inorganic compounds. Examples of the type of complexes which may be employed are the complexes of the aluminum halides and phenol, aromatics, olefins, cyclo-olefins and the fluid melts, such as aluminum halides with sodium chloride, potassium chloride and the like.

The temperatures to be employed in conducting the isomerization reaction are those well-known to the art, specifically a temperature in the range of between 100 to about 300 F. is suitable. The reaction may be conducted with the hydrocarbons in either the liquid or the vapor phase. Pressures employed will, therefore, be dependent on the conditions under which the hydrocarbon is employed.

The nature and objects of the present invention having been fully described and illustrated, what I Wish to claim as new and useful and to secure by Letters Patent is:

1. A process including the steps of introducing into a reaction vessel having exposed metal surfaces a mineral oil and causing said mineral oil to form a film on metal surfaces therein, maintaining the film at a temperature within the range of 150 F. to 300 F., introducing a vaporized aluminum halide into the vessel in an excess amount over that required to react with said oil, maintaining the aluminum halide vapors in contact with said oil film until a tenacious coating of carbonaceous material is deposited on surfaces within the vessel, subsequently introducing a hydrocarbon feed stock within the reaction vessel and reacting it therein with said excess aluminum halide.

2. In an isomerization process the steps of introducing a mineral oil into a reaction vessel adapted for conducting the isomerization reaction, causing the oil to form a film upon surfaces within said vessel, adjustin the temperature of said surfaces so that the film is at a temperature within the range of 150 F. to 300 F., introducing into the vessel sublimed aluminum halide in an amount greater than required to react with the oil film and contactin said sublimed aluminum halide with the oil film to form a tenacious coating of carbonaceous material, subsequently introducing a normal paraflin and a promoter within the reaction vessel and adjusting the temperature of the normal paraifin within the reaction vessel within the range of to 300 F. to cause isomerization of said parafiin in the presence of excess aluminum halide and said promoter.

3. A method in accordance with claim 2 in which aluminum chloride is employed as the aluminum halide in the reaction vessel.

. OTTO GERBES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,832,629 Hall Nov. 17, 1931 2,355,563 Schulze Aug. 8, 1944 1,512,420 Hall Oct. 21, 1924 

